• Journal of the Ergonomics Society of Korea
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• v.26 no.3
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• pp.27-33
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• 2007

The purpose of this study was to investigate influence of wrist position on the electromyographic(EMG) activities of the flexor digitorum superficialis (FDS) and extensor digitorum (ED) during drilling and pinch grip. Eighteen healthy subjects had been recruited and each subject performed two tasks (drilling and pinch grip) at three different wrist positions ($30^{\circ}$ flexion, neutral, $30^{\circ}$ extension). The EMG amplitude of each muscle was normalized to the amplitude in the maximal voluntary contraction (MVC). Repeated one-way ANOVA was used to compare the differences of EMG across wrist positions. The FDS EMG activity in both drilling and pinch grip was lowest at $30^{\circ}$ wrist extension and the highest at $30^{\circ}$ wrist flexion. The ED EMG activity was lowest when the wrist was neutral in both tasks. From the results of this study, we can conclude that the desirable wrist positions for drilling and pinch grip tasks are slightly extended or neutral position. Therefore, flexed wrist position should be avoided to reduce the excessive work load on the finger muscles during the tasks.

• Journal of Korean Institute of Industrial Engineers
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• v.37 no.3
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• pp.209-215
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• 2011

The objective of this study was to determine whether there are differences in hand muscle activities (APB : abductor pollicis brevis, ED : extensor digitorum, ECU : extensor carpi ulnaris, and EI : extensor indicis) and subjective discomfort according to the three mouse sizes (small, medium, large) and two task types (pointing and scrolling). The mouse size and task type showed significant interaction effects on the total NEMG (p = 0.004) and on the NEMG of the abductor pollicis brevis muscle (p = 0.001). The total NEMG and the NEMG of APB showed the highest value in the 'scrolling' task using the 'small' mouse. However, the NEMG of the EI was different according to the mouse size, and the 'small' mouse showed the lowest value. The subjective discomfort was the lowest in the 'medium' mouse, and all nine subjects preferred the 'medium' size. The hand-size related anthropometric variables showed different correlations according to the task type and mouse size with the NEMGs and subjective discomfort. The results of this study could be used as a basic information for the determination of the proper mouse size according to the hand size.

• Physical Therapy Korea
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• v.16 no.4
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• pp.37-43
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• 2009

This study compared the electromyographic activities and input performance of computer operators using a computer mouse and a trackball. Muscle activities were assessed at the upper trapezius (UT), middle deltoid (MD), extensor digitorum (ED), and first dorsal interosseous muscle (FDI). Twenty-six healthy subjects were recruited, and the test order was selected randomly for each subject. The task set was to click moving targets on a Windows program. The EMG amplitude was normalized using the percentage of reference voluntary contraction for UT and MD and the percentage of maximal voluntary contraction for ED and FDI. To analyze the differences in EMG activity, a paired t-test was used. UT muscle activities were significantly greater when the computer mouse was used (p<.05). FDI muscle activities were significantly greater when the trackball was used (p<.05). Using a trackball can reduce the load on the UT during computer work and help to prevent and manage work-related musculoskeletal disorders.

• Journal of Korean Physical Therapy Science
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• v.19 no.4
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• pp.53-59
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• 2012

Background : The purpose of the study was: to investigate muscle activation of upper arm according mouse shape. Methods : Twenty person(mean age : 23. 7) who have healthy condition was participated this study, we collected data of muscle activation using by EMG from upper trapezius(Tr), deltoid middle fiber(De), extensor digitorum(Ed), first dorsal interosseous(Di) during participants was performed click and drag according various mouse. Mouse shape was divided 4 level as follow shape 1 was very small, 2 was small, 3 was moderate, 4 was large. Data was analyzed ANOVA, independent t-test using by SPSS ver18.0. Results : There was significantly difference of muscle activation among each muscle according mouse shape in drag and click. In shape 1, 4, there was significantly difference of muscle activation of Tr, De, Ed between drag and click except Di. In shape 2, 4, there was significantly difference of muscle activation of all muscle between drag and click. Conclusion : We knew that extensor digitroum showed more higher muscle activation than other muscle in drag, first dorsal interoseous showed more higher muscle activation that other muscle in click. We suggest that mouse shape was very important factor in order to prevent skeletal muscular disorder for computer user, and mouse shape can reduce muscle fatigue during computer work.